Modern classrooms are increasingly diverse. Students vary in their academic abilities, personal interests, cultural and linguistic backgrounds, and previous experiences (Allen et al., 2013). To meet the varied needs of students, educators must adapt their instruction so all are able to find success. Modifying lesson plans and changing instruction based on student needs are forms of adaptive instruction (Hoffman & Duffy, 2016; Vaughn, 2019). This study explored the metacognitive processes of preservice teachers (PSTs) as they implemented adaptive instruction within their literacy lessons in a university reading center tutoring program. Adaptive instruction was examined through two lenses: first, as PSTs altered their lessons during instruction to meet students' immediate needs and second, as PST's used reflection to plan future lessons. By observing PSTs' adaptive instruction (or lack thereof), both during instruction and while lesson planning, insight was gained as to how PSTs became aware of and addressed their students' learning needs. Throughout this six-week study, PSTs were observed making adaptations to their instruction to support their tutees' success. Roughly 200 instructional adaptations were recorded overall. These adaptations ranged from adding an activity to changing the tutee's perspective. However, each adaptation served a purpose that was as unique as the child who benefited from its implementation. While instructional adaptations were the focus of the study, the PSTs were also observed implementing social emotional adaptations as well. When successfully implemented, the social emotional adaptations supported the tutees' eventual academic success. The results of this study could prove significant to the development of teacher preparation programs, especially those that occur in university reading centers. Additionally, the encouraging results of this study may incentivize universities to include coursework on adaptive instruction to prepare new teachers to meet the demands of increasingly diverse student populations. This study aims to support teacher educators as they continue to develop instructional programs that foster teacher professionalism, autonomy, and competence so vital for adaptive instruction. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]